The invention relates to a method and an apparatus for controlling the amount of fuel delivered by a fuel injection system to an internal combustion engine during engine starting.
The fuel injection system includes a first pulse generator circuit which generates preliminary pulses proportional to the aspirated air quantity and rpm. The system includes a multiplying circuit connected in series with the pulse generator circuit and both of these circuits contain capacitors which control multivibrators.
It is known to provide an electronic fuel injection system in which the duration of the control pulses for the various fuel injection valves is determined substantially from the load of the engine at any given time and the instantaneous rpm. A circuit, which will be explained in more detail below, uses these two variables to provide a so-called preliminary pulse. However, when the variables which define the duration of these pulses, i.e., the rpm and the load, assume unfavorable values, which can be derived from the air flow rate of the engine, the control pulses can fall in a critical domain where imprecise fuel metering may occur.
During the starting of an internal combustion engine, the prevailing engine speed and the aspirated air quantity are such that, in certain fuel injection systems, the air flow rate meter as well as the electronic circuitry which produces the preliminary injection pulses and will be called a control multivibrator in what follows, are insufficiently accurate for the requirements of smooth engine operation.
Thus, in order to obtain an optimum fuel-air mixture during the engine starting, the injection timing must take into account the engine temperature which, as is well known, plays a considerable role in the success of the starting process.